1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly to a plasma display panel that is adaptive for improving the uniformity of discharge.
2. Description of the Related Art
Recently, there has been developed various flat panel display devices with possible reduction in their weight and size, the weight and size have been the disadvantage of cathode ray tubes CRT. Such flat panel display devices include a liquid crystal display LCD, a field emission display FED, a plasma display panel PDP and an electro-luminescence EL panel, etc.
The PDP among these flat panel display devices is a display device using gas discharge and has an advantage that it is easy to be made on a large scale. A typical PDP is a three-electrode AC surface discharge PDP that has three electrodes, as shown in FIG. 1, and is driven by AC voltage.
Referring to FIG. 1, a discharge cell of the three-electrode AC surface-discharge PDP includes a first electrode 12Y and a second electrode 12Z formed on an upper substrate 10, and an address electrode 20X formed on a lower substrate 18.
The first and second electrodes 12Y and 12Z are formed of transparent material in order to transmit the light supplied from the discharge cell. On the rear surface of the first and second electrodes 12Y and 12Z, bus electrodes 13Y and 13Z of metal are formed in parallel with the first and second electrodes 12Y and 12Z. Such bus electrodes 13Y and 13Z are used in order to supply driving signals to the first and second electrodes 12Y and 12Z with high resistance value.
On the upper substrate 10 provided with the first and second electrodes 12Y and 12Z in parallel, there are deposited an upper dielectric layer 14 and a passivation film 16. Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer 14. The passivation film 16 prevents a damage of the upper dielectric layer 14 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This passivation film 16 is usually made from magnesium oxide (MgO).
A lower dielectric layer 22 and barrier ribs 24 are formed on the lower substrate 18 provided with the address electrode 20X. The surfaces of the lower dielectric layer 22 and the barrier ribs 24 are coated with a phosphorus 26. The address electrode 20X is formed in a direction crossing the first electrode 12Y and the second electrode 12Z. The barrier ribs 24 are formed in parallel to the address electrode 20X to prevent an ultraviolet ray and a visible light generated by a discharge from being leaked to the adjacent discharge cells.
The phosphorus 26 is excited by the ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. There is an inactive gas for a gas discharge injected into a discharge space defined between upper/lower plates and the barrier ribs, wherein the inactive gas can be He+Ne, He+Xe or He+Ne+Xe etc.
In such a conventional PDP, the first and second electrodes 12Y and 12Z are formed parallel in each discharge cell. The first electrode 12Y is supplied with a reset pulse, a scan pulse and a first sustain pulse. The second electrode 12Y is supplied with a second sustain pulse.
When the reset pulse is applied to the first electrode 12Y, the discharge cells are initialized. When the first electrode 12Y is supplied with the scan pulse, the address electrode 20X is supplied with data pulses synchronized with the scan pulses. At this moment, an address discharge is generated in the discharge cells which is supplied with a scan pulse and a data pulse.
After the address discharge is generated in the discharge cells, the first and second sustain pulses are alternately applied to the first and second electrodes 12Y and 12Z. When the first and second electrodes 12Y and 12Z are supplied with the first and second sustain pulses, there is a sustain discharge generated in the discharge cells where the address discharge is generated. In this sustain discharge, discharge time is determined by gray level values, and a picture is displayed in accordance with the gray level values.
On the other hand, the conventional first and second electrodes 12Y and 12Z occupy a broad area and are formed in parallel in the discharge cells. In this way, if the first and second electrodes 12Y and 12Z occupy a broader area, there is bigger power dissipation. Consequently, there is deterioration in the discharge efficiency of the PDP.
Referring to FIG. 3, the PDP according to another embodiment of the prior art includes an address electrode 32X, a first and a second electrode 31Y and 31Z formed in a direction crossing the address electrode, a first electrode 30Y extended from the first bus electrode 31Y, and a second electrode 30Z extended from the second bus electrode 31Z.
The first electrode 30Y is extended in a ‘T’ shape from the first bus electrode 31Y. The second electrode 30Z is extended in a ‘T’ shape from the second bus electrode 31Z. If the first and second electrodes 30Y and 30Z are formed in a ‘T’ shape, their total area can be reduced while keeping the electrodes long enough. Accordingly, the power dissipation decreases as much as the area of the first and second electrodes 30Y and 30Z is reduced, thereby improving the discharge efficiency. Also, in an example, the PDP with the ‘T’ shape electrode structure appears to be improved by about 15% in its light emitting efficiency.
Herein, in the conventional PDP with the ‘T’ shape electrode, the first and second electrodes 30Y and 30Z should be aligned between the barrier ribs 24 accurately. However, there occurs a movement of a few μm to several tens μm in the course of joining the upper and lower substrates 10 and 18 of the PDP. If there occurs any movement in the course of joining the upper and lower substrates 10 and 18, the first and second electrodes 30Y and 30Z cannot be formed at the center of the discharge cell as in FIG. 4.
And if the first and second electrodes 30Y and 30Z of a ‘T’ shape are not formed at the center of the discharge cell, the discharge is not uniformly generated for every cell. Also, there occur no normal address and sustain discharge. Additionally, there is a change caused in a discharge voltage characteristic, and a bad influence is given to a picture quality in the end.
In order to overcome these disadvantage, a PDP as in FIG. 5 has been proposed.
Referring to FIG. 5, the PDP according to still another embodiment of the prior art has at least two holes 42 formed on the first and second electrodes 40Y and 40Z of transparent electrodes. The holes 42 are disposed at regular intervals on the transparent electrode and should not overlap with the bus electrodes 41Y and 41Z.
The PDP according to still another embodiment of the prior art has an advantage of easy alignment as compared with the PDP as in FIG. 3 where the ‘T’ shape electrode should be located at the center of the discharge cell. And, power dissipation is reduced as much as the area in which the holes 42 are formed, and discharge efficiency is improved accordingly.
However, when the first and second electrodes 40Y and 40Z according to still another embodiment of the prior art are formed in the PDP, the areas where the first and second electrodes 40Y and 40Z overlap with the address electrode 44X are different from one another in the cells. In other words, the holes 42 as in FIG. 6 overlap with the address electrodes 44X in a range of 100%˜a few % for each discharge cell. Further, it is possible for the holes 42 not to overlap with the address electrodes 44X.
In this way, if the area where the address electrode 44X overlap with the hole 42 is different for each discharge cell, there occurs a lack of uniformity in the address discharge.